Advice on wire training tomatoes

I’m going to be wire/string-training some tomato plants this year after having seen it done with great success at a national trust garden last year.

I’ve learnt a lot about it, including that I need indeterminate varieties, how to attach the wire to the ground, how far apart to space plants etc.

However I am yet to find any info on how far to space plants from a wall if you are training them next to a wall. We have a lovely long south-facing stone wall to our house and it’ll be ideal for them, but first I need to find out how far out I need my wire so I can buy supports to attach to the fascia board that will bring the wire out far enough from the house.

Does anyone know? Or could take a better stab at a guess than a novice gardener like me?